A known type of biopsy needle has a needle-like obturator or stylet inside an outer sleeve, usually called a cannula, both extending from a hand-held housing and connected to separate operating handles. The free end of the obturator and the free end of the cannula are tapered for insertion into the body and the obturator has a tissue-receiving recess near its free end. The cannula covers the tissue-receiving recess in the obturator during their initial insertion into the body to a point close to where a tissue specimen is to be removed. Next, the obturator is pushed farther into the patient to extend the free end of the obturator from the cannula and expose the tissue-receiving recess to body tissue, which prolapses into this recess. Then, the cannula is pushed in so that it slides across the tissue-receiving recess in the obturator, severing the tissue specimen in that recess from the surrounding body tissue. Finally, the cannula and the obturator are withdrawn as a unit from the patient and the tissue specimen in the recess in the obturator is removed for analysis.
The biopsy needle is used in conjunction with an ultrasonic scanner having a display screen that shows the surgeon the position of the free ends of the obturator and the cannula in the patient's body.
One of the disadvantages of such biopsy needles is the relative slowness with which the obturator and the cannula can be safely operated manually after being inserted into the patient's body close to where the tissue specimen will be taken. When the tissue is relatively deep in the body and may have nerve endings, the slow sequential displacements of the obturator and the cannula can produce a substantial amount of perceived pain.
To overcome this problem, spring-operated biopsy needles have been used which, after insertion manually into the patient's body close to the desired location of the tissue specimen, produce relatively quick spring-powered movements, first, of the obturator, and then, of the cannula to capture a tissue specimen. These spring-operated biopsy needles have an automatic operation in which the tissue-severing movement of the cannula takes place immediately after the obturator is extended to receive body tissue in its recess, and the surgeon cannot change the brief time interval between exposure of the tissue-receiving recess in the obturator to the body tissue and the closing of that recess by the cannula to sever the tissue specimen in this recess. This time interval may be so brief that the specimen is damaged on the periphery because there was not sufficient time for the tissue to prolapse into the recess in the obturator before being severed by the cannula.
To offset this problem, one solution has been to lengthen this recess but this is unsatisfactory when sampling of a restricted area of the patient's body is desired. Also, it makes the captured tissue specimen too long to be ideally suited for pathology and the specimen is likely to have damaged cells near the ends.
Another disadvantage of such automatic, spring-operated biopsy needles is that they do not permit the surgeon to take a final view on the display screen of the ultrasonic scanner after the obturator has been extended to expose its specimen-receiving recess to the body tissue and before the cannula is extended to sever the tissue specimen and hold it in the recess in the obturator because the time interval between the two extensions is so brief.